This invention relates to a manufacturing method of a storage battery of the sodium-sulfur type by means of the thermocompression jointing method.
A storage battery of this type is a secondary battery of a high-temperature type and has been disclosed in U.S. Pat. No. 4,076,902. In such battery, sodium is utilized as an anodic reactant and sulfur or sodium polysulfide is utilized as a cathodic reactant, and they are separated by sodium ion conductive solid electrolytic tube to be actuated at a high temperature of about 300.degree. to 350.degree. C. Since both reactants are in molten state, it is necessary to completely seal the battery. In order to completely separate the reactants arranged internal and external sides of the solid electrolytic tube and to electrically insulate the cathode and anode, an .alpha.-alumina ring is jointed to an upper open end of the solid electrolytic tube by the use of solder glass, and metallic members of cathode and anode are separately jointed to said .alpha.-alumina ring. Jointing method of this case has been the thermocompression jointing method, in which the .alpha.-alumina and the metal have been connected and jointed by being applied pressure under heated condition. It has been known that firm junction can be obtained when the .alpha.-alumina and the metal are heated to approximately above 630.degree. C. with an aluminum O-ring therebetween under environment of vacuum or inert gas, subjected to pressure of about 200 kg/cm.sup.2 to 500 kg/cm.sup.2, and kept for more than about 20 minutes under these conditions. However, the above-mentioned conditions have a primary disadvantage that workability is extremely bad and productivity is poor because the work must be done under the environment of the vacuum or the inert gas. Further disadvantage is that firm junction is obtainable only in a part of the members even in case of jointing a columnar metal of small size for example as small as 10 mm in diameter, and thus, any junction is not obtained to cause easy peeling off in case of jointing a ring-shaped .alpha.-alumina of large size, for example as large as 50 mm in diameter, to a ring-shaped metal of the same diameter. Still further disadvantage is that, when the pressure is applied to an O-ring-shaped aluminum to deform it, it is not deformed uniformly and jointed positions are not stable.
This invention is intended to obviate all of the above mentioned disadvantages and to determine various conditions for thermocompression jointing useful practical use. First of all, this invention is intended to determine the conditions to obtain sound and uniform thermocompression jointing to a large .alpha.-alumina ring in air for the purpose of improving productivity and at the same time simplifying a thermocompression jointing equipment.